CNPC bought the rights to explore Block 58 in Peru's southern Amazon from Petrobras in 2014. The block then had proven reserves of about 2 TCF.

"The block that CNPC has ... will soon be declared viable with three to four trillion in proven reserves of gas," Peruvian President Pedro Pablo Kuczynski said in a speech at an energy event.

Peru's energy and mines minister has previously said that Block 58 likely has "important reserves" that would help ease concerns over whether a $5 billion natural gas pipeline being built in the region will find enough demand.

The government expects the company to make a detailed announcement next month when Chinese officials visit Peru.